With the increasing miniaturization and sophistication of electrical equipment such as mobile phones in recent years, it is demanded that the electronic devices used therein also be miniaturized. In order to meet these demands, it is indispensable to develop technologies for increasing the miniaturization and sophistication of device package, in addition to the miniaturization of the device itself. For technologies that achieve the miniaturization of the device package, various device packages employing a wafer-level package technology have been proposed, and it is expected that they will be applied to MEMS devices or image sensors (refer to Non-Patent Document 1).
For a package of a MEMS device or an image sensor device, it is necessary to provide a certain size of cavity in order to obtain space for driving micromachines or space for storing micro-lenses.
In the related art, as a method of forming the cavity in a wafer-level package, a method has been proposed, in which the substrates are bonded using previously patterned photosensitive resin as an adhesive, and the cavity is formed in a portion where the resin does not exist (refer to Non-Patent Document 2).
However, when a wafer-level package is manufactured using this method, since the thinning is performed by grinding the substrate after bonding in which the cavity is already formed, the weight applied during grinding is different between portions where the cavity is present and portions where the cavity is absent. Therefore, irregularities in the pattern depending on presence or absence of the cavity are generated on the surface of the substrate after the grinding. In some cases, a crack is generated in the substrates. This limits the thinning of the substrate.
[Non-Patent Document 1] Tatsuya ITO, “Electronic Materials,” January 2007, p. 60-64
[Non-Patent Document 2] S. Yamamoto, et al., “ICEP2006 Proceedings,” p. 259-264